This application requests five years of renewal funding for the Center for Prevention and Treatment Methodology. During its nine years of operation, the center has become nationally and internationally renowned for its cutting-edge research directly addressing methodological issues facing the drug abuse field. The over-arching theme of the proposed center is "Integrating innovative statistical approaches and drug abuse science." The four sub-themes that knit the scientific projects together are: Advancing methods for design and analysis in longitudinal research; optimizing use of resources in research design and behavioral interventions; using pragmatic Bayesian approaches to statistical computation, inference, and decision making; and improving causal inference. The proposed center includes five scientific projects, on the following methodological topics: optimizing the potency of behavioral interventions; using medical decision making in cost effectiveness analysis for drug abuse prevention; developing statistical methods for analysis of intensive longitudinal data; developing statistical methods related to development of adaptive interventions; and improving methods for missing data analysis, causal inference, and latent transition analysis. In addition, the center includes a Software Development and Computing Support Core. This center serves as a national resource in several ways: by acting as a leader in identifying emerging methodological issues in drug abuse research; by training the next generation of drug abuse methodologists; by attracting talented scientists to the field of drug abuse methodology; and by improving statistical methods used in the science of prevention and treatment and placing the improved methods in the hands of drug abuse scientists. Ultimately the efforts of this center lead to better behavioral intervention research. This in turn forms the basis of more effective drug abuse prevention and treatment interventions, with correspondingly greater public health impact.